Re-reading history from ZLE

Re-reading history from ZLE

[martin f krafft]

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Folks,

If a user widget modifies the history, e.g. appends a line using 
`print -s`, then the current ZLE instance does not find out about 
it: history expansion won't have access to it, and the `up-history` 
command doesn't "find" it.

```
% _test_hist() {
     print -s "echo foo"
     zle -M "The last line of history is now 'echo foo'
     zle reset-prompt
   }
% zle -N _test_hist
% bindkey '\et' _test_hist

   # now hit esc-t
% _
The last line of history is now 'echo foo'
```

The cursor is indicated by the underscore. If I execute 
`up-history`, I get the `bindkey` command line. `!$` will contain 
"_test_hist". Curiously, `!!` will run `echo foo`. I suspect this is 
due to those being different ways to access history for historical 
reasons, but it's an inconsistency nonetheless.

Is there a reason why `reset-prompt` shouldn't re-initialise ZLE's 
understanding of history?

Thanks,

-- 
@martinkrafft | https://matrix.to/#/#madduck:madduck.net
  
"the worst part of being old is remembering when you was young."
                               -- alvin straight (the straight story)
  
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Re: Re-reading history from ZLE

[Bart Schaefer]

On Wed, Aug 24, 2022 at 8:26 AM martin f krafft <madduck@madduck.net> wrote:
>
> Is there a reason why reset-prompt shouldn't re-initialise ZLE's understanding of history?

History isn't updated until ZLE exits (accept-line, etc.).  The
"current event" is not actually in the history, it's treated specially
as a pending entry; almost anything you do with a widget (including
print -s) is effectively part of that pending entry.

There is one exception:  The "fc" command updates the history
immediately.  So if you rewrite your widget as ...

_test_hist() {
    fc -R =(<<<"echo foo")
    zle -M "The last line of history is now 'echo foo'
    zle reset-prompt
  }

... then you'll get what you want, including seeing the value of %h
(history number) in your prompt increase by one.

Beware that "fc -R" may ignore lines beginning with ": " because it's
attempting to intuit whether the file is using extended history
format, and if you're adding a multi-line entry you'll want to prefix
all the newlines with backslashes, etc.